Wireless, remote control, motorized window coverings are activated by a control signal generated and sent by a transmitter. As explained in U.S. Pat. No. 4,712,104 to Kobayashi, the control signal is usually converted into one of audio, radio (RF), or light (either visible or, more preferably, infrared (IR)) energy, and transmitted through the air. When a button on a remote transmitter is pushed, the control signal comprising one of these types of energy is generated. The control signal sent by the transmitter may comprise a carrier signal which modulates either a continuous waveform or, more preferably, a sequence of spaced apart pulses. In those cases where spaced apart pulses are used, the pulses may either be coded, or they may comprise a sequence of pulses having substantially identical pulse widths and a constant pulse repetition frequency (PRF).
Each wireless, remote control motorized window covering system is provided with at least one transducer which converts the transmitted energy into electrical signals. In the case of an audio signal, the transducer is a microphone. In the case of RF signal, the transducer is likely to be an antenna, which may comprise an electromagnetic coil tuned to the carrier frequency. Finally, in the case of a light signal, the transducer is typically a photodiode, a photoresistor or a phototransistor.
As the signal travels from the transmitter to the transducer, it may become slightly corrupted. For instance, in the case of an acoustic signal, environmental noise in frequencies of interest, may be added to the signal. In the case of a light signal, light from other sources may be added to the received signal. Further corruption may take place as the transmitted signal is converted by the transducer into an electrical signal. This is because all transducers, however precise, cannot output an electrical signal which perfectly replicates the incoming transmitted signal. Usually, the electrical signal from the transducer will vary slightly from what was transmitted.
In addition to being corrupted, the signal may have also been modulated before transmission, as explained above. Together, these factors result in a signal that is distorted, and may be unintelligible to a decision circuit, described further below. To help correct some of this distortion, the electrical signal from the transducer is usually preprocessed before it is interpreted by a decision circuit. The goal of this preprocessing is to convert the electrical signal from the transducer to a form that can be used, and is less likely to be mis-interpreted, by the decision circuit. This process is loosely referred to as "cleaning up" the signal.
Cleaning up a signal from a transducer may involve filtering and demodulating a signal, as is often necessary with RF and IR signals. It may also involve waveshaping using comparators, inverters and triggers which have hysteresis-like input/output relationships, as disclosed in U.S. Pat. No. 5,275,219 and Canadian Patent No. 1,173,935 to Yamada, both of which are directed to motorized window systems which respond to daylight. In the case of IR signals, an integrated IR receiver, having a photodiode or a phototransistor, signal amplifiers, bandpass filters, demodulators, integrators and hysteresis-like comparators for waveshaping, perform such a function. The IS1U60, available from Sharp Electronics, is such a receiver, and can be used in remote control operations.
As stated above, in a remote control system, the cleaned up control signal is presented to a decision circuit. The role of the decision circuit is to determine a) whether the cleaned up control signal is valid, i.e., whether or not the signal content is such that the system should respond, and b) what, if any, response should be taken, in view of the control signal content and other status information.
The decision circuit comprises additional sensors, switches and registers, which keep track of such things as the direction of last motion, the position of the window covering relative to its travel extremes, and other status information. The decision circuit may be formed entirely from a combination of discrete analog and digital components, in which case the decision circuit is said to be hardwired. Alternatively, the decision circuit may include a microprocessor, microcontroller, or equivalent, in which case the decision circuit is said to be programmable. As is known to those skilled in the art, incorporating a microprocessor, or the like, allows for more complex decision making with the control signals and other status information.
All decision making circuits, whether or not they incorporate a microprocessor, are connected to a motor circuit adapted to drive a DC motor. Although the exact implementation of a motor circuit may differ, they all serve to connect the source of power, be it a battery, a solar cell, or even an AC-to-DC transformer, to the motor to operate the window covering. A typical motor circuit is disclosed in U.S. Pat. No. 4,618,804 to Iwasaki. In this circuit, two signals from the drive circuit are used to activate a pair of transistors. In such a motor circuit, upon receipt of an "UP" motor signal from the decision circuit, current flows from the voltage source, through a first transistor, the motor, and a second transistor to drive the motor in a first direction (e.g., clockwise). And, upon receipt of a "DOWN" motor signal, current flows from the voltage source through a third transistor, the motor, and a fourth transistor to drive the motor in an opposite direction (e.g., counterclockwise).
The power supply for a motorized window covering system may originate from an alternating current (AC) source, as shown in U.S. Pat. No. 3,809,143 to Ipekgil. In such case, one plugs into a wall socket and a transformer, or the like, is used to convert the AC into DC. As an alternative to using an AC power source, the power supply may comprise a battery, which may be recharged by a solar cell and/or by plugging into an AC source. U.S. Pat. No. 4,664,169 to Osaka discloses such a battery-operated lift system which moves a bottommost supporting slat relative to a headrail.
In wireless, remote-controlled motorized systems having an AC power source, there is little concern about designing the system to minimize energy consumption. This is because the AC source provides, for all practical purposes, virtually unlimited power. On the other hand, when a battery, especially one that cannot be recharged, is used, the current draw of the system becomes a design concern. This is because the transducer must always be available to receive a transmitted control signal. Also, the preprocessing, decision making and motor drive circuitry must be prepared to respond immediately, which usually means that they are, at the very least, in a "standby mode", which also draws at least some current.
In the case of battery powered systems, there are three general approaches to conserving battery power. One approach is to use low-power, discrete analog and digital components which are on at all times, whether or not a valid control signal is received. This is the approach taken in U.S. Pat. No. 5,495,153 to Domel et al., which calls for using low dark-current phototransistors, and low-power logic devices such as NAND gates, counters, flip flops, power saving resistors, and the like. A second approach is to cycle one or more components on and off while waiting for a valid signal. This is the approach taken in U.S. Pat. No. 5,134,347 to Koleda, which calls for turning an IR receiver on for a brief period of time, and then allowing it continue to stay on longer if it receives a valid signal. The approach taken in Koleda is based on well-settled techniques for reducing the duty cycle of a receiver powered by a battery, as disclosed in U.S. Pat. No. 4,101,873 to Anderson et al. Finally, the third approach of conserving battery power is to use a solar cell to continuously recharge the batteries. U.S. Pat. No. 4,644,990 to Webb discloses a photosensitive energy conversion element which recharges batteries used to supply power to automatic system for tilting blinds.
To operate a window covering, the motor is typically placed in a headrail where it is hidden from view. A rod, to which the motor is operatively engaged, is rotatably mounted in the headrail. When the rod rotates, cords connected at one end to the rod, and also connected to the shade or blinds, can be wound either directly on the rod or on a spool arranged to turn with the rod in a lift system. U.S. Pat. No. 4,550,759 to Archer shows such a system for controlling the tilt of a blind, and U.S. Pat. No. 4,856,574 to Minami shows a motorized system for controlling the lift of a horizontal slat.
The extent of travel for a window covering can be limited by a counter, which uses dead reckoning to keep track of the number of rotations of the motor or the rod, relative to a stored counter value. In such case, the rotating wheel, or the like interrupts an optical or a magnetic path, and these interruptions are counted. Such systems are shown in the aforementioned Minami '574 reference.
As an alternative to "dead reckoning", limit switches may be used to control the extent of movement of the window covering. Limit switches are mechanical switches which are activated by engagement with a member of the system during the latter's operation. In the typical case, the limit switches are stationary and are abutted by a movable member of the motorized system. U.S. Pat. No. 4,727,918 to Schroeder discloses the use of limit switches in the headrail to control the tilt of a blind. Along similar lines, Danish Patent No. 144,894 to Gross discloses the use of limit switches in the headrail to control the lift of a shade.
It should be noted here that we have used the word "shade" to generically describe a window covering which could be raised and lowered. This word encompasses such window coverings as venetian blinds comprising horizontal slats, pleated shades, accordion shades, and the like. As is known to those skilled in the art, pleated and accordion shades are typically formed from a lightweight fabric, and thus are often lighter than the more rigid slats. Because of this, it is generally accepted that mechanisms having sufficient torque to raise and lower horizontal slats, can also raise and lower lightweight shades.
Finally, in the typical remote control motorized system, the transducers, circuitry, motors, and servo mechanisms used to operate one type of window covering, can often be adapted to operate other types. For instance, as explained in International Publication WO 90/03060 to Roebuck, a motor/servo arrangement capable of opening and closing vertical slats and also drawing them, can readily be adapted to venetian blinds (horizontal slats) and the like. Similarly, EPO 381,643 to Archer shows that a DC motor mounted in headrail and connected to rotatably mounted rod can lift horizontal slats or pleated shades with virtually no modifications.
The prior art also includes systems which combine a large number of the features discussed above. For instance, there are wireless, remote-control lift systems having a headrail-mounted DC motor which winds a lift cord around a rod, and which has additional novel features. One such example is the battery-powered device of U.S. Pat. No. 5,029,428 to Hiraki, which is placed between the panes of a double-pane window. Another, is the IR-controlled, AC-powered, microprocessor-based device of Japanese Laid-open application 4-237790 to Minami, which provides for a programmable lower limit for the shade using the transmitter.